A Penetration Viscometer for Determining Viscosity of Glass

An apparatus was constructed for determining the viscosities of small flat pieces of glass from the rate of penetration of a cylindrical indenter. A diagrammatic sketch of the apparatus is given in Fig. 1. The essential parts of the apparatus are; (1) A cylindrical indenter, (2) A device to supply the load to the indenter, (3) An optical system to magnify the penetration distance of the indenter into the glass, (4) An electric furnace to provide a suitable constant temperature enclosure. Using the NBS 710 glass the relation between the rate of penetration and viscosity of glass was determined with this viscometer. This relation is given by a formula of the type Wt/η=AP2+BP in which P: penetration depth, η: viscosity of glass, W: supplied load, t: time and A, B: constants.This method is adapted to the measurement of the viscosity η in the range of 104∼1012 poises with experimental accuracy of about Δlogη=±0.1. And then the viscosity of some chalcogenide glasses was measured in the range of 106∼1011 poises.